MythBusters Episode 129: Greased Lightning
Air Date: October 28, 2009
If a person tries to put out a stovetop grease fire by pouring a small amount of water on it, a fireball exceeding 30 feet (9.1m) in diameter will result.
busted
Adam and Jamie started stove fires with three different cooking materials: canola oil, peanut oil, and lard. The ratio of oil to water was 8 to 1 in each case, with 64 US fluid ounces (1,900 mL) of oil and 8 US fluid ounces (240 mL) of water. In each case, a large fireball formed when the water was poured in, due to the sudden formation of steam which propelled the burning oil upward. No fireball reached higher than 25 feet (7.6 m). To investigate further, Adam and Jamie did some smaller-scale tests, varying the oil/water ratio and the shape of the cooking pot. The latter had no apparent effect on the fireball height, but they decided to use a 2:1 ratio (2 US qt/1,900 mL of oil, 1 US qt/950 mL of water) for further full-scale work in a mockup kitchen set. Under these conditions, they were able to get a 30-foot (9.1 m) fireball; however, they declared the myth busted because the original 8:1 ratio did not generate the stated result. In a further test, they set up a shelf to drop an unopened can of soup into the oil, reasoning that having all the water-based material at the bottom of the pot would more effectively launch the oil when it vaporized and exploded. The result was a fireball with an estimated height of 100 feet (30 m).
It is possible to extinguish a grease fire with enough water.
confirmed
Adam called in a firefighting helicopter, which dropped 500 US gallons (1,900 L) of water on the grease fire and successfully extinguished it.
A person can detonate a block of C-4 (and escape) by placing it in a microwave oven and heating it for one minute.
busted
The Build Team set up three microwave ovens, each of which contained a different C-4 device: one unaltered block, one with wiring similar to that used in the film, and one with both wiring and a blasting cap. Using a remote-controlled bomb disposal robot, the team set each oven to run for 60 seconds at full power. The unaltered block did not heat up appreciably, while the one with only the wiring caught fire but did not detonate (though the door of that oven did burst open). The wiring/cap device exploded violently after only a few seconds of heating, due to sparks arcing across the metal wires and touching off the blasting cap. Since a person placing this bomb in a microwave would be unable to get to safety before it exploded, the team declared the myth busted.
(This myth is based on a scene from the film Grosse Pointe Blank.)
A block of cheese can be fired from a cannon with enough force to shred a ship’s sail.
confirmed
The Build Team evaluated three different cheeses for hardness, stiffness, and elasticity: Edam, smoked Gouda, and Garrotxa. They set up a canvas sail made with period-accurate materials and methods, and fired one sample of each cheese at it. Edam, the softest of the three, bounced off the sail without damaging it; Gouda, the hardest, was too brittle and broke up into fragments as soon as it left the barrel; but the Garrotxa, having the right mix of hardness and elasticity, remained intact and punched a hole in the canvas. Even though the exact type of cheese did not match the accounts, the team declared the myth confirmed.
(This myth is based on accounts of a 19th-century South American naval battle in which a Uruguayan commander was forced to use slabs of Dutch Edam instead of cannonballs when the ammunition ran out.)
i’m positive that anyone who knows the original myth (enough to burn the facial hair off your face will result) was satisfied with the experiment, but not with the conclusion.
October 29, 2009 at 11:41 PMSo the exact type of cheese not matching is acceptable, but a large fireball not being precisely 30 feet is unacceptable?
October 30, 2009 at 9:03 AMthis is not a true test, you did not allow for the wind , the fireball was blown sideways wich would impede its upward travel,, if it was done in a windlass situation it would make it to the 30 foot mark…….
November 5, 2009 at 9:10 AMI agree with Robert. I was looking for a place to post the same response. It clearly shows how the wind is a factor.
November 14, 2009 at 10:24 PMYes, the wind inhibited the rise of the fireball in the air…looking at the footage and estimating for the wind you had two of the three (lard excluded) that WOULD have made 30ft.
November 14, 2009 at 10:31 PMAs far as lighting C4 in microwave that should be CONFIRMED. They didn’t know how to use a microwave. Set the first stage to 0 power (how many minutes before explosion) the second stage full power. Every microwave that has a electronic timer can do this.
November 15, 2009 at 6:45 PMIf you want to verify this type
Time 10 power 0 then Time 30 Start
It will give you 10 seconds of 0 power then 30 seconds of Full power to set off the C4.
In the real word you would set it for 5 – 10 minutes for 0 power to get away not 10 seconds.
On Oil fires Disaster . I think use different temperatures of water. Example:100℃ water ,16℃-20℃ water and ice
November 22, 2009 at 2:29 AMThe fireball reaching exactly 30 feet is very much beside the point. How many kitchens have 30 foot ceilings on them?
November 24, 2009 at 5:51 PMI still think that a 30 ft fire ball is still plausible. They used peanut oil which has a flash point of about 450°F, But what about Almond Oil which has a flash point of about 495°F or Avocado oil with a flash point of 520°F? Even Extra Light Olive oils can have a slightly higher flash point than Peanut oil and it is commonly used in cooking.
November 30, 2009 at 8:54 AMIf you all think you can do better why don’t you try and then film the results and post them on youtube? What is the saying “either put up or shut up”?
December 2, 2009 at 8:00 PMThis is the first time I’ve commented on one of the myths. The wind clearly moved the fireball away from the 30 feet mark. They really screwed up on this one!
January 30, 2010 at 11:11 AMI have to chime in as well regarding this myth. The experiment was clearly done on a windy day, and as a result the fireballs were blown sideways. If you measure the height of the fireballs along the diagonal, you will get 30 ft (or very close) for the first two tests.
February 7, 2010 at 8:34 PMRe C4 in microwave (Grosse Point Blank), to me it does appear that the C4 is NOT set off by the microwave itself but is set off by the microwave stopping.
February 20, 2010 at 6:34 AMMy rationale is that there is a glass bulb containing mercury attached to the C4, the centrifugal force of the rotating plate keeps the mercury away from the wires, (clearly visible when Martin Blank looks into the microwave during the gun battle) when the microwave stops rotating the dish the mercury moves towards the centre, touching the wires therefore completing the circuit and BOOOOOOM!